Apparatus and method for spraying herbicide on weeds in a cotton field

ABSTRACT

Weeds growing around the bases of the stalks of cotton plants growing in a row in a cotton field are sprayed with herbicide without spraying the cotton stalks or wasting herbicide on bare ground. The cotton plants are adequately mature that their stalks exhibit a significantly different spectral reflectance characteristic than the weeds typically growing amid the cotton. The cotton plants are adequately tall that the majority of the leaves of the cotton plants are disposed outside the area which can be sprayed using an electronically-controlled valve and nozzle. Light is transmitted toward an object (a cotton stalk, a weed, or soil) in the row and the reflected light is analyzed. If the object has a spectral characteristic of a growing weed, then the valve is activated and the object is sprayed with herbicide. If the object does not have the spectral characteristic of a growing weed (such as the spectral characteristic of a woody cotton stalk or of soil), then the valve is not activated and the object is not sprayed with herbicide.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/276,002, filed Jul. 15, 1994 (now U.S. Pat. No. 5,585,626), which inturn is a continuation-in-part of application Ser. No. 08/149,867 (nowU.S. Pat. No. 5,389,781), filed Nov. 10, 1993, which in turn is acontinuation of application Ser. No. 07/920,942, filed Jul. 28, 1992(now U.S. Pat. No. 5,296,702).

FIELD OF THE INVENTION

The present invention relates to the optical detection of objects. Moreparticularly, the present invention relates to applying herbicide ontoweeds in a field of cotton.

BACKGROUND INFORMATION

U.S. Pat. No. 5,296,702 discloses structures and methods fordifferentiating living plants from soil. Living plants have a spectralreflectance characteristic in regions of the electromagnetic spectrumwhich differs from the spectral reflectance characteristic of soil. Bytransmitting light of a first wavelength and light of a secondwavelength onto an object and detecting the relative magnitudes of thereflected light of the two wavelengths, it can be determined whether theobject has the spectral reflectance characteristic of a living plant orthe spectral characteristic of soil. To conserve herbicide inagricultural spraying operations, living plants so differentiated fromsoil are sprayed with herbicide and the bare ground (which does not havethe spectral characteristic of a living plant) is not sprayed. Cottonplants are, however, living plants. A device is therefore desired whichwill spray herbicide onto weeds growing between and around the cottonplants without killing the cotton plants themselves.

SUMMARY

Weeds growing around the bases of the stalks of cotton plants aresprayed with herbicide without spraying the cotton stalks or wastingherbicide on bare ground. The cotton plants are adequately mature thattheir stalks exhibit a significantly different spectral reflectancecharacteristic than the weeds typically growing amid the cotton. Thecotton plants are adequately tall that the majority of the leaves of thecotton plants are disposed outside the area which can be sprayed usingan electronically-controlled valve and nozzle. Light is transmittedtoward an object and the reflected light is analyzed. If the object hasa spectral characteristic of a growing weed, then the valve is activatedand the object is sprayed with herbicide. If the object does not havethe spectral characteristic of a growing weed (such as the spectralcharacteristic of a woody cotton stalk or of soil), then the valve isnot activated and the object is not sprayed with herbicide.

This summary does not purport to define the invention. The invention isdefined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a proximity determining sensor.

FIGS. 2A-2C are cross-sectional views of a light detector of the sensorof FIG. 1.

FIGS. 3A-3E are plan views of a light detector illustrating an operationof the sensor of FIG. 1.

FIGS. 4A and 4B are views of an operation of the sensor of FIG. 1.

FIG. 5 is circuit diagram showing one embodiment of a circuit of thesensor of FIG. 1 which generates a signal indicative of a distance to anobject.

FIG. 6 is a diagram illustrating different spectral reflectioncharacteristics of a living plant, a dead leaf, soil, and a parasiticweed over a wavelength range of 400-1100 nm.

FIGS. 7A-7D are diagrams illustrating a light pipe in accordance withsome embodiments.

FIGS. 8A and 8B are diagrams illustrating the spraying of herbicidearound the base of a tree.

FIGS. 9A and 9B are diagrams illustrating a determination of thelocations of rows of crop plants.

FIG. 9C is a diagram illustrating guidance of an implement such as acultivator through a field of row crop plants using a hydraulicactuator.

FIG. 10 is a diagram illustrating how weeds growing in the rows ofcotton plants are detected and sprayed without spraying the cottonplants.

FIGS. 11A and 11B illustrate a method and apparatus for sprayingherbicide onto weeds in a cotton field without spraying the stalks ofthe growing cotton plants.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a proximity determining sensor 1. Proximitydetermining sensor 1 comprises a source of light 2 which generates light3, a light beam forming lens 4 which forms light 3 into a light beam 5,a detector lens 6, and a light detector 7. Light beam 5 is aligned indirection A. Detector lens 6 has an optic axis in direction B. If, forexample, light from light beam 5 reflects off an object located at pointP1, then reflected light from the light beam will be incident on lightdetector 7 at a near image position 8. If, on the other hand, light fromlight beam 5 reflects off an object located at a distant point P5, thenreflected light from the light beam 5 will be incident on the lightdetector 7 at a far image position 9. Reflections of light from lightbeam 5 at several intermediate positions P2-P4 are also illustrated inFIG. 1. Sensor 1 may, for example, be moved in direction C with respectto the surface 10 of the ground in an open field so that light beam 5 isscanned over surface 10.

In one specific embodiment of FIG. 1, the light of light beam 5 isgenerated by a plurality of light emitting diodes arranged in a row.Only one of the light emitting diodes is illustrated in FIG. 1 becausethe row of light emitting diodes extends in the direction perpendicularto the plane illustrated. Light beam forming lens 4 is a cylindricallens which has a longitudinal axis which extends in the direction of therow of light emitting diodes. Light beam 5 therefore is a relativelythin sheet of light having a first dimension which extends in thedirection perpendicular to the illustrated plane and having a seconddimension, the direction of travel of the light, which extends indirection A.

In some embodiments, light detector 7 is a silicon PIN photodiode ModelNo. SL3-2, manufactured by UDT Sensors, Inc., Hawthorne, Calif. Othersuitable photodetectors may be used. In some embodiments, a chargecoupled device (CCD) may be used. In some embodiments, lens 4 is acylindrical lens approximately 3 inches long and approximately 1 inchwide having a focal distance of approximately 0.8 inches, available fromUnited States Precision Lens. In some embodiments, detector lens 6 is aplano-convex lens approximately 1.5 inches in diameter having a focaldistance of approximately 1.5 inches available from United StatesPrecision Lens. The angle between directions A and B is about 7.1degrees, the lateral distance between light source 2 and light detector7 is about 2.8 inches, and the distance between light detector lens 6and light detector 7 is about 2.5 inches.

FIG. 2A is a cross-sectional view of the light detector 7 of FIG. 1showing near image position 8 and far image position 9 in greaterdetail. The image plane of the detector surface of light detector 7 isslanted with respect to the optic axis of light detector lens 6 in orderto maintain focus of the light arriving from the various objectpositions P1-P5.

FIG. 3A is a plan view of the detector surface of the light detector 7of FIG. 1 looking up into light detector 7 in the direction opposite todirection B. Light detector 7 has an active area 11 and a chip boundary12.

FIGS. 4A and 4B are diagrams illustrating sensor 1 at two points in timewhen sensor 1 is moved in direction C with respect to the surface 10 ofa field. As illustrated in FIG. 4A, when at a first point in time lightfrom light beam 5 is reflected off a surface of a relatively tall livingplant 14A at a distance D1 from sensor 1, an image of the reflectedlight is formed on light detector 7 at image position 13. As illustratedin FIG. 4B, when at a second point in time sensor 1 has moved farther inthe direction C with respect to the surface 10 of the field, light fromlight beam 5 is reflected off a surface of a relatively short livingplant 14B at a distance D2 from sensor 1. An image of the reflectedlight is formed on light detector 7 at image position 15. Accordingly,the position of the image of the reflected light on light sensor 7 isindicative of the distance of the reflecting object. The angle betweenthe detector axis and the light beam axis is set so that light reflectedfrom light beam 5 strikes the center of the light detector 7 for anobject located at a predetermined distance from sensor 1. This allowsfor a large variation in sensor-to-object distance.

FIG. 2B is a cross-sectional view of one embodiment of light detector 7.Light detector 7 actually comprises a plurality of smaller detectors7A-7E. If the image created by the light reflecting off the relativelytall living plant 14A is formed at image position 13 on detector 7C,then a corresponding signal will be generated on an output terminal ofdetector 7C. If, on the other hand, the image created by the lightreflected off the relatively short living plant 14B is formed at imageposition 15 on detector 7B, then a corresponding signal will begenerated on an output terminal of detector 7B. The distance from thesensor 1 to the object 14A, 14B is determined by identifying from whichparticular detector of detectors 7A-7E the signal emanates.

FIG. 2C is a cross-section view of another embodiment of light detector7. Light detector 7 comprises a single detector, the near image position8 being at one end of the detector active area, the far image position 9being at an opposite end of the detector active area. Such a lightdetector has an additional anode terminal, the relative magnitude of thesignals present on the two anode terminals being indicative of therelative position of the image between two ends of the active area ofthe detector. The distance from the sensor 1 to the object 14A, 14B istherefore determined by comparing the relative magnitudes of the twoanode signals due to the reflected image.

FIG. 5 is a circuit diagram showing one embodiment of a circuit 16 ofsensor 1 which generates a signal on terminal 19, the voltage of thesignal being indicative of a relative distance between a reflectingobject 14A, 14B and sensor 1. The specific embodiment illustrated inFIG. 5 comprises a first trans-impedance amplifier 20, a secondtrans-impedance amplifier 21, a difference amplifier 22, a summingamplifier 23, and a divider 24. Anode terminals 25 and 26 of lightdetector 7 may, for example, correspond with near image position 8 andfar image position 9 of a single detector light detector 7,respectively. Light detector 7 has a cathode 27 coupled to an LC circuit27A. Light detector 7 can be reverse biased or can be operated in thephotovoltaic mode as shown. The LC circuit 27A is provided todiscriminate sunlight as explained below. The magnitude of an analogvoltage generated on the output terminal 19 of divider 24 isproportional to a distance to a reflecting object. This distanceinformation in the form of an analog voltage is converted to a digitalrepresentation before being processed in a microcontroller. In someembodiments, output terminal 19 is coupled to an analog-to-digitalconverter input pin of a microcontroller (not shown).

Not only is light reflected from light beam 5 incident on light detector7, but light from other sources may also be incident on light detector7. When, for example, the sensor 1 is operated in broad daylight in anopen field, sunlight is reflected off objects and back up into sensor 1.Moreover, because the sunlight is not focussed into a beam, reflectedsunlight is incident on the entire detecting surface of light detector7. Sensor 1 distinguishes reflected sunlight from reflected light frombeam 5 using techniques disclosed in U.S. patent application Ser. No.07/920,942 (now U.S. Pat. No. 5,296,702), the contents of which areincorporated herein by reference. In one embodiment, light 3 from lightsource 2 is modulated with a modulation signal having a frequency. TheLC filter circuit 27A is tuned to the modulation frequency and thereforepasses energy at the frequency of the modulation signal and attenuatesenergy at other frequencies. Accordingly, the component of the signaloutput by light detector 7 which is due to reflections of light beam 5is distinguished from components of the signal output by light detector7 which are due to the more slowly varying ambient sunlight.

In some embodiments, a phase difference between the signal output onoutput terminal 19 of the circuit of FIG. 5 and a modulation signal usedto modulate the light 3 emitted from light source 2 is used by amicrocontroller to determine whether an illuminated object is a plant.The phase of the signal oscillating in LC circuit 27A is determined bythe phase of the radiation received. If more radiation modulated with afirst phase is received, the signal oscillating in LC circuit 27A willhave a phase relatively closer to the first phase whereas if moreradiation modulated with a second phase is received, the signaloscillating in the LC circuit 27A will have a phase relatively closer tothe second phase. Both distance information and spectral characteristicinformation are therefore provided by the same circuit of FIG. 5. Inother embodiments, a separate circuit such as is set forth in U.S.patent application Ser. No. 07/920,942 (now U.S. Pat. No. 5,296,702) isprovided to determine whether the illuminated object is a plant so thatdistance information is provided by the circuit of FIG. 5 and spectralcharacteristic information is provided by a separate circuit.

In some embodiments, a plurality of units such as sensor 1 is aligned ina row such that the row of units senses objects disposed in a narrowilluminated strip and such that each individual unit senses acorresponding section of the strip. The light of light beam 5, however,may diverge somewhat in the direction perpendicular to the planeillustrated in FIG. 1 so that a band of an object illuminated by beam 5at near position P1 has a relatively short length whereas that same bandilluminated by beam 5 at far location P5 has a relatively long length.In order to control the field of view of the unit over a range of objectdistances and prevent overlap of the fields of view of adjacent units,an image mask 28 is disposed between detector lens 6 and light detector7.

FIG. 3B illustrates five images 29A-29E corresponding with light of beam5 reflected from positions P1-P5, respectively. FIG. 3C illustrates animage plane mask 28. An opening of image plane mask 28 has a first edge28A which is non-parallel with respect to a second edge 28B opposite thefirst edge. FIG. 3D illustrates the images 29A1-29E1 which are incidentupon the detector surface of light detector 7 due to the operation ofimage plane mask 28. Image 29E1 corresponds with the same illuminatedobject distance on a distant object located at position P5 as doesobject image 29A1 on a close object located at position P1. FIG. 3Eillustrates the image incident on the detecting surface of lightdetector 7 moving back and forth across the detecting surface as adistance between an object illuminated by light beam 5 is moved towardand away from sensor 1.

In accordance with some embodiments, light of light beam 5 reflectedback into sensor 1 is also analyzed to determine a spectralcharacteristic of an object from which the light reflected. Depending onthe spectral reflectance characteristic detected, a determination can bemade as to whether the object is a plant. Accordingly, a sensor inaccordance with some embodiments develops information indicative ofwhether an object illuminated by light beam 5 is a plant in addition toinformation indicative of a distance between the sensor and the object.

FIG. 6 is a diagram illustrating how certain living plants, a dead ordying plant, soil, and a parasitic weed reflect light having differentwavelengths over the wavelength range of 400-1100 nm. Lines 30, 30A,30B, 30C and 31 of the graph of FIG. 6 indicate spectral characteristicsof a living plant of a first species A, a parasitic weed, a living plantof a second species B, a dead or dying plant and soil, respectively. Bydetecting a relative reflectance of light off an object at twowavelengths (for example, 670 nm and 750 nm) it is possible todistinguish light reflected from living plants from light reflected fromsoil. By detecting a relative reflectance of light off an object at twowavelengths (for example, 645 nm and 750 nm), it is possible todistinguish light reflected from living chlorophyll bearing plants fromlight reflected from certain parasitic weeds. By detecting a relativereflectance of light off an object at two or more wavelengths (forexample, 430 nm, 575 nm and 750 nm), it is possible to distinguish lightreflected from various living chlorophyll bearing plants of certainspecies from other chlorophyll bearing plants of other species. It ispossible to distinguish the difference between rice and water grass inthis fashion. A more detailed description of a technique for determiningwhether an object is a living plant or is soil is set forth in U.S.patent application Ser. No. 07/920,942 (now U.S. Pat. No. 5,296,702).

Therefore, in accordance with some embodiments, light 3 comprises lighthaving a first wavelength and light having a second wavelength. Thelight having a first wavelength is modulated with a first modulationsignal whereas the light of the second wavelength is modulated with asecond modulation signal. In a preferred embodiment, the firstmodulation signal has the same frequency as the second modulation signalbut is offset in phase with respect to the second modulation signal. Inaccordance with the technique disclosed in U.S. patent application Ser.No. 07/920,942 (now U.S. Pat. No. 5,296,702), the relative magnitude ofthe component of a signal output by light detector 7 due to the light ofthe first wavelength with respect to the component of the signal outputby light detector 7 due to the light of the second wavelength isdetermined. A relative magnitude corresponding with corresponding pointson line 30 is indicative of a reflection off a plant whereas a relativemagnitude corresponding with corresponding points on line 31 isindicative of reflection off soil. Although one technique for developinginformation indicative of whether an object is a plant is set forth herefor illustrative purposes, it is to be understood that other techniqueswhich take advantage of the different reflectance characteristics ofdifferent objects may be employed in sensor 1.

Large object size to image size reductions (high demagnification) whenthe object is close to the light detector lens can be difficult torealize. Light rays converging to the image focus are at a largeincluded angle and the depth of field is small. Light detector lens 6may therefore be a somewhat expensive lens and it may be difficult toadjust lens 6 mechanically in order to achieve a proper focus of thereflected light onto the detecting surface of the light detector 7. Toovercome these difficulties, the image is focussed at a convenient lowerdemagnification with a lower power light detector lens 6 and anon-imaging tapered light pipe is used to effect a spatial compressionof the light of the image where distance determination or proximitysensing is not performed by light detector 7. Accordingly, system costis reduced and mechanical adjustment tolerances are relaxed.

FIG. 7A shows a light pipe 32 disposed between image mask 28 and lightdetector 7. Light detector 7 comprises a plurality of light detectorchips. Due to the inclusion of light pipe 32, light detector lens 6 neednot focus on the relatively small detector surface. Rather, a ray oflight 133 passes into light pipe 32 as illustrated in FIG. 7B. FIG. 7Cis a top-down view illustrating a ray of light 134 passing through lightdetector lens 6, through the opening in image mask 28, into light pipe32, and onto light detector 7. FIG. 7D is a side view illustrating a rayof light 135 passing through light detector lens 6, through the openingin image mask 28, through light pipe 32, and to light detector 7. Due tothe tapered shape of the light pipe 32, the light reflected off theobject reflects down the light pipe and onto the smaller light detectorsurface.

The methods set forth below do not constitute an exhaustive treatment ofall uses of the present distance determining technique but are merelyillustrative.

Method #1 Spraying Weeds Growing in the Ground Around Trees

FIGS. 8A and 8B are diagrams illustrating an orchard sprayer 33 forspraying weeds growing in the ground around trees. Orchard sprayer 33comprises four sensors denoted T, A, B and C in FIGS. 8A and 8B. Each ofthe sensors comprises a plurality of light emitting diodes which emits anarrow long light beam. The narrow long light beams emitted from sensorsA, B and C are directed toward the ground as illustrated in FIG. 8B suchthat strips of the ground A, B and C are scanned by light beams fromsensors A, B and C, respectively, as a means for moving 34 moves theorchard sprayer with respect to the tree 35. The light beam emitted fromsensor T is, on the other hand, directed in a substantially horizontaldirection so as not to illuminate weeds on the ground but so as to bereflected off tree 35 as illustrated in FIG. 8A.

Each of the three sensors A, B and C is coupled to a corresponding rowof electrically-controlled valves, pumps, or injectors (not shown) sothat a plant detected by one of the sensors will be sprayed by nozzlescontrolled by that sensor. In one embodiment, each of theelectronically-controlled valves (such as part number AM2106 availablefrom Angar Scientific) has an associated spray nozzle and thereforeforms an electronically-controlled spray nozzle.

In order to spray weeds on the ground around tree 35 without sprayingthe tree itself, a distance to tree 35 is determined by sensor T as themeans for moving 34 moves the orchard sprayer past the tree. A shorttime after sensor T detects an object having a spectral reflectancecharacteristic indicative of a living plant (which in this case would betree 35) at a distance between distance DT1 and DT2, the spray nozzlesof sensor A are disabled so that tree 35 will not be sprayed. The spraynozzles coupled to sensors B and C, however, remain enabled so thatweeds growing in the ground in strips B and C will be sprayed. Sensors Band C only cause objects having a spectral characteristic of a livingplant to be sprayed and therefore do not waste herbicide by spraying thebare ground. After the means for moving 34 propels the orchard sprayerfarther so that sensor T detects tree 35 at a distance between distanceDT2 and DT3, sensors A and B are disabled leaving only sensor C todetect and spray weeds in strip C. Again, sensor C only causes objectshaving a spectral reflectance of a living plant to be sprayed. When theorchard sprayer has moved to the opposite side of the tree, the spraynozzles for the corresponding strips are enabled in reverse order assensor T detects the distance to tree 35 getting larger, therebyspraying weeds in the ground around tree 35 and not spraying herbicideonto the tree itself.

In the illustration, sensors T, A, B and C are mounted in a staggeredconfiguration on means for moving 34 in the direction of travel. Thesensors A, B and C would therefore be disabled and enabled anappropriate amount of time after the tree is detected by sensor T sothat weeds in the corresponding strip will be sprayed right up to theedge of the tree without spraying the tree. The speed of the means formoving 34 is therefore detected and used to determine when to enable anddisable the spray nozzles. In order to prevent the spray frominterfering with the optics of the plant detecting operation, the weedsare not sprayed when they are detected but rather are sprayed at a latertime as explained in U.S. patent application Ser. No. 07/920,942 (nowU.S. Pat. No. 5,296,702).

Method #2 Spraying Trees and not Spaces Between Trees

In accordance with another embodiment, an orchard sprayer detects a treeand then controls spray nozzles to spray the tree with a chemicalmaterial (such as pesticide and other foliar applied materials) so thatthe chemical material is not wasted in the spaces between trees. Becausea distance sensor is able to determine whether or not the reflectedlight has a spectral characteristic of a living plant, such an orchardsprayer distinguishes non-plant objects from living trees, therebyovercoming the above described problem of spraying barns and peopleassociated with prior art orchard sprayers. In some embodiments,material flow is switched on and off depending on the total biomassdetected in the field of view and the distance to the biomass. Fluidpressure, nozzle configuration, nozzle direction and other parameters ofthe spraying operation are also automatically adjusted to accommodatethe particular size, density and distance to the biomass. This techniqueis also usable for selectively dispensing herbicide on weeds alongroads, highways and railroad tracks.

Method #3 Row Crop Middle Selective Weed Sprayer

Many crops grow in rows where the spacing between rows is fixed by theplanting or seeding implement. Such row crops include corn, soybeans,tomatoes and cotton. The space between adjacent rows is referred to asthe "middle" and often should be kept free of weeds in order to optimizecrop yield and to minimize harvesting problems. Traditionally thismiddle has been kept free of weeds by mechanical cultivation. Thistechnique has limitations. First, tilling or breaking up the soilrequires large equipment and therefore large amounts of energy. Second,so-called "cultivator burn" results from getting too close to the rowwith the cultivator tines and damaging plant roots. Third, tilling opensthe soil to the air thereby allowing moisture to escape and making thesoil subject to erosion from wind and rain.

Spraying weeds in the middles with herbicide may therefore be considereda more desirable method of eliminating weeds from the middles. Twoprincipal difficulties with spraying weeds are cost of the herbicidematerial and the potential of contaminating the environment withexcessive chemicals. Both of these problems are addressed by aspects ofthe present embodiment.

Weeds in middles are generally found in patches ranging from a fewinches across to a few feet across. It is generally not practical for aspray vehicle operator to turn the sprayer off and on, each time a patchof weeds is encountered. Therefore a preferred technique is to relyheavily on preemergence herbicide to discourage weed seeds fromgerminating and then later spraying a continuous blanket of postemergence herbicide in the middles to eliminate any weeds whichgerminated despite the preemergence herbicide. Selective spraying usingthe optical detection technology described previously eliminates theneed for preemergence herbicide and minimizes the application ofpostemergence herbicide because only weeds are sprayed and significantamounts of bare soil is not sprayed. Considerable cost savings canresult.

FIGS. 9A and 9B show a means for moving 34 (in this case a tractor)outfitted with a plurality of sensors 36 and a plurality ofsolenoid-operated spray nozzles (not shown). The sensors are mounted ona boom such that a strip of the field perpendicular to direction oftractor movement D is illuminated with modulated light. Distanceinformation and information on whether an illuminated object hasspectral reflectance indicative of crop plant, weed plant or soil issent to a central digital processor (not shown). By storing pastinformation on which sensors detect the most objects having specialcharacteristics of plants and which sensors detect the most objectshaving heights consistent with the expected crop height, the centraldigital processor determines which illuminated objects having specialplant characteristics are crop plants in rows 37 and which are randomlyscattered weeds 38. Accordingly, the central digital processor disablesthe spray nozzles located over the rows 37 of crops. As a result, onlythe weeds 38 in the middles are sprayed. The row crops 38 are notsprayed and herbicide is not wasted on the bare ground in the middles.

Method #4 Row Crop Row Selective Crop Sprayer

In accordance with another embodiment, rows of crops are located asdescribed above. Rather than spraying the middles with herbicide,however, the crop plant in the rows are sprayed with foliar nutrients,pesticide, selective herbicide or water.

Method #5 Vehicle or Implement Guidance

In many farming operations, a vehicle and/or implement is guided throughrows of crops in a field. In cultivating row crops, for example, thecultivator implement is guided as fast as possible through the rows ofcrops so that the cultivator tines come as close as possible to thecrops plants without damaging the crop itself. Manually guiding thevehicle and/or implement with respect to the rows is a demanding andtedious task. If, for example, the cultivator strays too close to a row,a section of the row of crop plants may be uprooted. Various automaticimplement and vehicle guidance systems therefore have been developed toguide vehicles and implements with respect to rows of crops. None ofthese automatic vehicle guidance systems has, however, enjoyed broadmarket acceptance.

A furrow is formed between adjacent rows at the time the row crop isplanted. "Mole balls" are physical weights which are dragged in such afurrow. As the vehicle moves through the field, the weight of mole ballkeeps the mole ball in the furrow between rows. If the vehicle orimplement strays toward either row, switches or valves are actuatedwhich operate a hydraulic cylinder to adjust the direction of travel ofthe vehicle or implement.

Another vehicle guidance technique involves the use of wires or similarmechanical devices which make actual physical contact with the row cropplants. The mechanical touching devices are connected to switches whichin turn control a hydraulic or other means of redirecting the vehicle orimplement.

Still other vehicle guidance techniques use ultrasonic sonar and/orinfrared detectors. An infrared method disclosed in U.S. Pat. No.5,279,068 directs infrared radiation toward plants in two adjacent croprows. The two magnitudes of the reflected infrared radiation arecompared and the vehicle or implement is steered to keep the magnitudesof the two signals balanced thereby keeping the vehicle or implementcentered between the two rows. This technique is believed to haveproblems due to weeds in the middle reflecting and giving incorrect dataand due to voids in the row of crop plants not reflecting and notproviding sufficient data. Accordingly, the above-described techniquesexhibit problems when faced with situations involving fields withoutwell contoured furrows, crop plants which are damaged by physicalcontact with the guidance device, and voids in crop rows where plantshave not survived.

These problems are overcome in accordance with certain of the describedembodiments. As set forth above in connection with FIGS. 9A and 9B,sensors 36 are mounted on the vehicle or implement. The sensors may bedisposed to illuminate and therefore follow only one row. Alternatively,the sensors may illuminate and follow multiple rows as is illustrated inFIGS. 9A and 9B. Each sensor may output three types of information: 1)information indicative of whether there is an object at a suitable rangefrom the sensor in the field of view, 2) information indicating whetheran object in range in the field of view has spectral reflectanceproperties indicative of a plant crop, a weed, or another object, 3) andinformation indicative of a distance to the object. In some embodiments,the magnitude of total reflected radiation detected is the informationindicating that an object is at a suitable range from the sensor in thefield of view. A digital processor coupled to the sensor examines theoutput of each sensor periodically and stores the information in memory.The digital processor, with the aid of software composed for thispurpose, compares the current data being gathered from the sensors tothe data stored in memory. From the information available, the digitalprocessor makes very accurate predictions on row location based onobject sizes, object heights, ground topology and/or plant locations andspectral reflectance properties. Because the crop plants were planted atthe same time in an accurate row pattern, they are probably of asomewhat consistent size. The processor is therefore able to determineaccurately which plants are crop and which plants are weeds. Knowingwhich plants are the crop allows the processor to plot a line whichrepresents the centerline of the crop row 37. In some embodiments, thisinformation is put into a format which is accepted by currentlyavailable vehicle guidance systems.

In some embodiments, an implement is guided (for example, a cultivator)with respect to rows in a field.

FIG. 9C is a diagram illustrating a plurality of sensors 36 coupled to adigital processor 90. Digital processor 90 comprises a multi-inputanalog-to-digital converter 90A, microcontroller 90B and memory 90C.Digital processor 90 determines the locations of the rows of crop plants91 and moves the implement 92 to the left or the right via valve drivers93, valves 94 and hydraulic actuator 95. If, for example, the implement92 is a cultivator, the digital processor 90 controls the location ofthe tines of the cultivator to uproot weeds 96 but to leave crop plants91. Vehicle 97 may or may not be guided by the digital processor 90through the rows of crops in the field. Voids in crop rows where plantshave not survived does not cause the guidance system to fail.

In other embodiments, a vehicle guidance system does not use spectralinformation but rather uses only distance to object information. Forexample, where dead plants are to be harvested or where a vehicle orimplement is to be guided through a recently planted field in which theseeds have not yet germinated, the distance information may be used tomap soil contours and to locate furrows and rows accordingly.

Method #6 Mapping Objects in a Field

Some parts of a field may have different types of soil, may receivedifferent amounts of runoff, may receive different amounts of directsunlight, may have different types of pests, and may be subject to otherenvironmental factors which affect plant growth in different ways. Ifinformation bearing on these different environmental factors could beeasily gathered, such information could be used in determining how andwhen to till, to fertilize, and to harvest. It could be determined, forexample, that certain parts of a field should be planted with one typeof crop whereas other parts of the field should be planted with anothertype of crop.

In accordance with one embodiment, information to make a map of a fieldis gathered automatically when the field is traversed for anotherpurpose such as cultivating. Information indicative of whether a stripof a field illuminated with modulated light contains soil, living cropplants, weeds or other objects, and the size of these plants or otherobjects is supplied by a sensor to a data storage device. The samesensor unit is able to determine the amount of organic material in thesoil. As a tractor, picker, combine or other means for moving sweeps thesensor and data storage device across the field, the data storage devicerecords the soil/plant information and distance information on a storagemedium. A hard disk drive may be used. In some embodiments, the datastorage device also receives position information from a globalpositioning system (GPS) device so that the detected characteristics ofthe field are mapped to the corresponding geographical locations in thefield. In this way, characteristics of the field can be gathered,downloaded from the data storage device, and later analyzed. In fact,the analysis can be done in real time and application rates adjustedsimultaneously. Using this technique, multiple field maps gatheredduring multiple growing seasons and for different types of crops can becompared and analyzed.

Method #7 Cotton In-Row Weed Sprayer

Many row crops are grown in rows with plants in each row spaced only afew inches apart. Rows may be spaced 30 to 40 inches apart. Typicallyplant spacing within each row is uneven so that the canopy of adjacentplants often grow into each other or conversely there could be gapswhere no plants exist. In such a situation, it is possible to identifythe centerline of the planted row (as discussed above) but it may not bepossible to rely upon the plant spacing within the row for purposes ofeliminating weeds growing between crop plants in the row. It istherefore desirable to discriminate between weeds and crop plants usingmore than plant/soil location information.

Cotton is a crop where it is desirable to discriminate between cropplants in rows and weeds between the crop plants in order to selectivelyeliminate weeds without damaging the crop plants. When the cotton plantis less than a few weeks old, its stalk is soft green tissue which issomewhat translucent to near infrared light. The stalk reflects stronglyin the infrared portion of the spectrum and it appears to have much thesame spectral reflectance as a weed might. It is therefore difficult todiscriminate the cotton crop from the weed plants. At this stage of thecrop development, one weeding method is to spray the rows with acontinuous band of selective chemical herbicide which can be toleratedby the cotton crop (e.g., MSMA). Another method measures the differencesin spectral reflectance, at certain wavelengths, of cotton plants versusthat of the weed plants. Certain weed types can be discriminated fromcotton plants on the basis of a different spectral reflectance andtreated accordingly.

At a later stage, the cotton stalks become opaque but generally stillhave the spectral characteristics of weeds. At this point it is possibleto discriminate cotton stalks in the rows from weeds in the rows. FIG.10 shows a first sensor 39 located on one side of a row of cotton stalks41 and second sensor 40 located on the other side of the row. In thisembodiment, sensor 40 is oriented to receive only light modulated bysensor 39 and sensor 39 is oriented to receive only light modulated bysensor 40. Light reflecting off an object surface in the crop rowcenterline has an angle of reflection in excess of 45 degrees. In thespecific embodiment illustrated, the angle of reflection exceeds 90degrees.

Because the vertical cotton stalks 41 typically do not provide areflecting surface that reflects light from one side of the row to theother, and because the weeds 41 having a different reflective surfaceprofile do provide such a reflecting surface, the sensor does not detectmodulated light reflected from cotton stalks but does detect modulatedlight reflected from weeds 42 in the cotton rows. The weeds 42 cantherefore be selectively eliminated without damaging the cotton stalks41.

At a later stage, the cotton stalks become woody and cease to be similarin spectral reflectance to weeds. The cotton crops can therefore bediscriminated from the weeds using the normal spectral reflectancetechnique described earlier. Weeds in cotton can be eliminated usingelectronically-controlled plant-eliminating devices including automatichoes and electronically-controlled herbicide applying spray nozzles.

FIGS. 11A and 11B are diagrams illustrating a method and apparatuswhereby weeds 100 which are growing around the bases of cotton stalks101 are sprayed with herbicide without spraying substantial amounts ofherbicide onto the cotton plants themselves. In FIGS. 11A and 11B, themajority of the leaves (not shown) of the cotton plants are disposedabove the upper extent of the cotton stalk illustrations. Rather thantransmitting light from one unit disposed on one side of a row of cottonplants and detecting reflected light in another unit disposed on theother side of the row (see FIG. 10), plant detecting techniques such asthose disclosed in U.S. Pat. No. 5,296,702 are employed to transmitlight 102 from a unit 103 toward an object 104 in or adjacent a row ofcotton plants 105 and to receive in unit 103 a portion of that lightwhich reflects off the object. The object can, for example, be a growingweed, a cotton stalk of a growing cotton plant, or bare ground. Light102 is transmitted and received on the same side of the row 105 betweenrow 105 and an adjacent row, row 105A. Distance determining techniquesset forth in U.S. patent application Ser. No. 08/276,002 (the subjectmatter of which is incorporated herein by reference) may also beemployed. In some embodiments, light 102 travels toward object 104 inrow 105 at an angle 106 in the range of 30 to 60 degrees with respect toa surface 107 of the field.

The cotton plants in the rows are adequately mature that their stalksare woody and have a spectral characteristic which differs significantlyfrom a spectral characteristic of a typical weed which would be growingin a cotton field. In one example, the growing weeds are Purple Nutsedgeplants. In one example, the cotton plants are the Pima or Acalavarieties of cotton, are at least six weeks old, and are at least eightinches tall. MSMA herbicide is used.

If unit 103 detects the reflected light and determines that the object104 has the spectral characteristic of a growing weed (see FIG. 11A),then unit 103 causes herbicide to be sprayed onto the object 104. Anysuitable technique for spraying herbicide onto a plant in a field can beused. If, on the other hand, unit 103 detects the reflected light anddetermines that the object 104 has another spectral characteristic (seeFIG. 11B), then unit 103 does not cause herbicide to be sprayed ontoobject 104. Spectral characteristics other than the spectralcharacteristic of the growing weed include the spectral characteristicof woody cotton stalks and the spectral characteristic of soil. Becausethe majority of the leaves of the cotton plants is disposed above thearea illuminated by the light 102 and is outside the area which can besprayed, the majority of the leaves of the cotton plants is not sprayedwith herbicide.

As illustrated, both weeds located in the line of the row and weedslocated somewhat outside the line of the row are illuminated with light102 and sprayed. Unit 103 may comprise one light emitting diode,photodetector and spray nozzle set or may comprise a plurality of suchsets arranged in a row. If a single light emitting diode, photodetectorand spray nozzle set is used, then the spectral information obtainedwill be the average of the spectral characteristics of all objects inthe field of view of the set.

The unit may be moved through the cotton field parallel to the row 105of cotton plants on an implement attached to and/or drawn by a tractoror other suitable vehicle. In some embodiments there is one unit foreach row, whereas in other embodiments there are two units for each row,one disposed on each side of the row. In some embodiments unit 103 usesan electronically-controlled valve (part number 9X37 manufactured by KIPIncorporated) to control the application of herbicide. A magnetizedmetal filter may be employed to remove particles from the herbicidewhich might otherwise plug the valve.

Method #8 Detecting Dissimilar Objects in a Flow of Grain

Harvesting equipment is particularly prone to being damaged by pickingup rocks and other hard objects. A sensor (as described above) is usedto detect the presence of rocks or metal fragments in the flow of cropmaterial in harvesting equipment and to disengage power before damagecan result. The field-of-view of a sensor capable of determining aspectral reflectance of an object is aligned across the flow of the cropmaterial in the harvesting equipment. The background may be a pipe, wallor panel having a particular spectral reflectance, the flow of cropmaterial flowing between the sensor and the background. Crop materialflowing through the field of view of the sensor results in a certainspectral signature being detected by the sensor. In the event that thecrop has a spectral characteristic of a living plant 30 such as is shownin FIG. 6, introduction of a rock into the flow of crop material willresult in a substantially different spectral characteristic beingdetected. The difference in spectral characteristics is used to detectthe rock and to disengage power from the harvesting equipment.

Method #9 Detecting a Parasitic Weed in a Field of Crop Plants

A parasitic weed is discriminated from a crop plant. Line 30A in FIG. 6shows the spectral reflectance of a parasitic weed known as Dodderversus wavelength. Dodder germinates from a seed which may lie dormantin the ground for up to ten years. When about 2 to 3 inches tall, theDodder plant finds a host (the host could be a safflower plant, a tomatoplant, or an alfalfa plant). The young Dodder plant attaches itself tothe host, grows up into the host plant, severs its own roots to thesoil, and lives parasitically from its host. When mature, the Dodderplant looks much like a ball of orange colored spaghetti. Being orange,it has a different spectral reflectance characteristic in the visiblespectrum which differentiates it from a chlorophyll bearing host plant.Because Dodder has very little chlorophyll, the spectral reflectancecurve for Dodder does not have as large of a chlorophyll absorption dipat 670 nanometers as do host plants having larger amount of chlorophyll.

In accordance with one embodiment, spectral reflectance at twowavelengths is measured. As illustrated in FIG. 6, an ordinary cropplant typically has a larger difference between the reflectance atwavelengths 670 nanometers and the reflectance at 770 nanometers thanthe parasitic Dodder weed. The magnitude of the difference in spectralreflectance at these two characteristic wavelengths is used todiscriminate light reflecting from the parasitic weed from lightreflecting from the crop plant. After the parasitic weed is identifiedin the field and distinguished from the crop plants, the parasitic weedis automatically eliminated by selective spraying or selectivecultivation. Over a period of years, all parasitic weeds and seeds ofparasitic weeds are eliminated from the field.

Although the present invention has been described by way of thepresently described specific embodiments, the invention is not limitedthereto. Adaptations, modifications and various combinations ofdifferent aspects of the specific embodiments may be practiced withoutdeparting from the spirit and scope of the invention. The term "light"is not limited to visible light, but rather includes infrared radiation,ultraviolet radiation, and electromagnetic radiation of other suitablefrequencies. The above description is presented merely for illustrativeinstructional purposes and is not intended to limit the scope of theinvention as set forth in the following claims.

We claim:
 1. A method, comprising:(a) transmitting light onto a firstobject in a field, said first object being a living plant other than acotton plant; (b) detecting a portion of said light which reflects offsaid first object and obtaining spectral information indicative of saidfirst object; (c) transmitting light onto a second object in said field,said second object being a stalk of a living cotton plant; (d) detectinga portion of said light which reflects off said second object andobtaining spectral information indicative of said second object; (e)differentiating said first object from said second object using saidspectral information indicative of said first object and said spectralinformation indicative of said second object; and (f) using anelectronically-controlled valve to apply herbicide onto said firstobject and to apply substantially no herbicide onto said second object.2. The method of claim 1, further comprising:(g) moving a source of saidlight and said electronically-controlled valve together through saidfield, said source of light generating said light of step (a) and saidlight of step (c).
 3. The method of claim 1, wherein a first row ofcotton plants and a second row of cotton plants are disposed in saidfield, said light being transmitted in step (c) from a location betweensaid rows.
 4. A method, comprising:(a) transmitting light onto a firstobject in a field, said first object being a living plant other than acotton plant; (b) detecting a portion of said light which reflects offsaid first object and obtaining spectral information indicative of saidfirst object; (c) transmitting light onto a second object in said field,said second object being a stalk of a living cotton plant; (d) detectinga portion of said light which reflects off said second object andobtaining spectral information indicative of said second object; (e)differentiating said first object from said second object using saidspectral information indicative of said first object and said spectralinformation indicative of said second object; and (f) using anelectronically-controlled valve to apply herbicide onto said firstobject and to apply substantially no herbicide onto said second object,wherein at least six weeks have passed between the time said cottonplant germinated and the time step (f) is performed.
 5. A method,comprising:(a) transmitting light onto a first object in a field, saidfirst object being a living plant other than a cotton plant; (b)detecting a portion of said light which reflects off said first objectand obtaining spectral information indicative of said first object; (c)transmitting light onto a second object in said field, said secondobject being a stalk of a living cotton plant; (d) detecting a portionof said light which reflects off said second object and obtainingspectral information indicative of said second object; (e)differentiating said first object from said second object using saidspectral information indicative of said first object and said spectralinformation indicative of said second object; and (f) using anelectronically-controlled valve to apply herbicide onto said firstobject and to apply substantially no herbicide onto said second object,wherein said cotton plant is at least eight inches tall.
 6. A method,comprising:(a) transmitting light onto a first object in a field, saidfirst object being a living plant other than a cotton plant; (b)detecting a portion of said light which reflects off said first objectand obtaining spectral information indicative of said first object; (c)transmitting light onto a second object in said field, said secondobject being a stalk of a living cotton plant; (d) detecting a portionof said light which reflects off said second object and obtainingspectral information indicative of said second object; (e)differentiating said first object from said second object using saidspectral information indicative of said first object and said spectralinformation indicative of said second object; and (f) using anelectronically-controlled valve to apply herbicide onto said firstobject and to apply substantially no herbicide onto said second object,wherein said field has a surface, and wherein said light is transmittedin step (c) such that said light travels toward said second object at anangle in the range of 30 to 60 degrees with respect to said surface. 7.The method of claim 1, further comprising:(g) transmitting light onto athird object in said field, said third object being soil; (h) detectinga portion of said light which reflects off said third object andobtaining spectral characteristic information indicative of said thirdobject; (i) differentiating said third object from said first objectusing said spectral characteristic information indicative of said thirdobject; and (j) using said electronically-controlled valve to applysubstantially no herbicide onto said third object.
 8. A method,comprising:detecting light reflecting off a cotton stalk in a field andobtaining first spectral information therefrom; detecting lightreflecting off a growing plant in said field other than a cotton plantand obtaining second spectral information therefrom; distinguishing saidcotton stalk from said growing plant using said first and secondspectral information; using an electronically-controlled valve to applyherbicide onto said growing plant and to apply substantially noherbicide onto said cotton stalk.
 9. The method of claim 8, furthercomprising:moving a source of said light and saidelectronically-controlled valve together through said field, said sourceof light generating said light reflecting off said cotton stalk and saidlight reflecting off said growing plant.
 10. Structure, comprising:meansfor distinguishing a cotton stalk of a growing cotton plant in a fieldfrom another growing plant in said field, said another growing plantbeing a plant other than a cotton plant; and means for applyingherbicide onto said another growing plant without applying a substantialamount of herbicide onto said cotton stalk.
 11. The structure of claim10, wherein said another growing plant is growing between adjacentcotton plants in a row of cotton plants.
 12. The structure of claim 10,further comprising:means for moving said means for distinguishing andsaid means for applying together through said field.
 13. The structureof claim 10, wherein said means for distinguishing comprises:means fortransmitting substantially monochromatic light of a first wavelength;means for transmitting substantially monochromatic light of a secondwavelength; and means for detecting light.
 14. The structure of claim10, wherein said means for distinguishing transmits light from a firstside of a row of cotton plants and detects a portion of said light fromthe same side of said row, said cotton stalk being a part of a cottonplant growing in said row.